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The hunt for cold - Model discussion (late November)


Paul
Message added by Paul

If you're hunting for cold potential in the model output, this thread is for you. But if you'd like to look more widely at the models, please head over to the general model discussion thread.

This is a model related thread, so a general, frequent theme of the model output is a given, but it will not be strictly enforced:

  • Some topic drift, humorous responses etc are fine
  • Posts likely to lead the thread off on an entirely off topic tangent are not ok. For example (but not solely limited to): Posts entirely or mainly about Met Office, BBC or media forecasts with little or no model context, and posts solely asking for a weather forecast in a specific location.
  • Posts which start with something like 'I know this is off topic but ...' are not ok.
  • Posts which break the forum guidelines are not ok (eg trolling, troll-hunting, weather guilt tripping, overly defensive/aggressive, abusive, disrespectful to others)

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield

gFS still running with heights exiting the ESB pushing towards Greenland in various ways.still imo looks like a good route to any cold

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Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.
11 hours ago, Catacol said:

No charts today from me - but a request for a bit of resilience in this thread over the coming few days. I don't think the ridge next week is going to hold: there isn't the background forcing to sustain it, and it really is just an echo from the final phase of the last pacific wave. Let's not throw the toys out if/when battleground scenarios next week get watered down. It is possible we might have a transient snow event - but to my eye it is really only going to be transient.

It is very clear that torques are reengaging now, and that we are going to see a spike in AAM once again over the coming 1 - 2 weeks. This is going to begin the process of enhancing westerlies at 30N and scrubbing them out at 60N. The jet will drop south in that time span, and the extension of the pacific jet specifically will help reengage a high lat block pattern. Signs of this will begin to appear in NWP modelling in the next few days at the extended range, but it will take until the end of the week until we see NWP pick up on this progression consistently. In the meantime don't mourn the shunting east of the scandy ridge in its upcoming form too much. 

I'm confident of this longer term progression and confident that we will see blocking entrench in the second half of this month driven by the new pacific wave. And this is a pattern that will sustain into January. Great news for all snow lovers. The really interesting bit now is just how the impact of this very favourable pacific pattern will combine with top down impacts from a strat warming event. The Siberian high / Aleutian low Nino combo looks to be a pattern that is going to sustain over the medium term at least - and with such sustained pressure it looks unlikely that the vortex can hold its ground. But will it shatter or just wobble badly? I don't think anyone can be confident of that process yet - all the keen minds in other places are agreed on the magnitude of the hit that is coming - but I've not read a single punter willing to put a bet down on just how this will play out. Pacific forcing will not be overridden by the much weakened vortex in its forecast state - but will the shape of upper winds help reinforce that trop led pattern? If it does then we could be in for a very special period of weather. If it doesn't then cold will still come, but less dramatic in its impacts.

Top post. Thanks, Catacol.

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Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.
6 hours ago, Daniel* said:

Such a laughable difference from UKMO 12z to 00z doesn’t look any good for undercut but nowhere near as progressive to 12z with doomed Scandi block, seemingly a lot of struggle in this area.

ED61708F-7484-41C6-B8F2-C6D6C962EFFF.thumb.jpeg.c50199bd89a1992d91f9dcb820a12279.jpegE63F7689-8B0F-40C3-BAA5-A7C022FC31DD.thumb.gif.c20c70d2bed0ff3e34bf3089523f4b48.gif

Late Wednesday into Thursday is the day of the big battle, 60/40 possibility of some short-lived transient snowfalls around then I'd suggest. The on-the-ground specifics as to who gets it and how much will only be answered as late as Wednesday, as that snow is such an oh-so-tricky thing to forecast, but it's coming to a few of us.

Edited by gottolovethisweather
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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.

A northerly again modeled for around Christmas. Miles off, of course, but shown on a few runs now.

christmas.png

Edited by MattStoke
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Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth

No pushing in the queue at the bookies

1A6D6222-28FA-4260-AE73-6134B60F4DF1.png

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Posted
  • Location: Essex Riviera aka Burnham
  • Weather Preferences: 30 Degrees of pure British Celsius
  • Location: Essex Riviera aka Burnham

Well the 0z ECM looks better in the shorter to medium term with some frontal battles and possibly snowy events for some and cold hanging around till' next weekend but in the longer term post day 10 looks worse...those depressions keep on coming!

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

These are the sort of temperature values we need to be seeing up top.

https://www.instantweathermaps.com/GFS-php/strat.php?run=2018120906&var=TMP&lev=1mb&hour=384

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Posted
  • Location: Canmore, AB 4296ft|North Kent 350ft|Killearn 330ft
  • Location: Canmore, AB 4296ft|North Kent 350ft|Killearn 330ft
4 minutes ago, That ECM said:

No pushing in the queue at the bookies

1A6D6222-28FA-4260-AE73-6134B60F4DF1.png

Current odds being offered on a white Christmas .... always worth a flutter based on these long shot charts 

610681ED-4E56-4CE0-8611-7CD06A91094F.png

Edited by c00ps
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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
8 minutes ago, MattStoke said:

A northerly again modeled for around Christmas. Miles off, of course, but shown on a few runs now.

christmas.png

And the GFS's grand finale:

Netweather GFS Image

And the 00Z GFS ensemble, as I'm sure the uncertainty hasn't disappeared in only 6 hours!

GEFS Ensembles Chart

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Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea
19 minutes ago, Ed Stone said:

And the GFS's grand finale:

Netweather GFS Image

And the 00Z GFS ensemble, as I'm sure the uncertainty hasn't disappeared in only 6 hours!

GEFS Ensembles Chart

Defo a drop off towards the end. Might be worth placing Christmas day or Boxing day as the day for a pattern change to colder weather.

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Posted
  • Location: Brighton, East Sussex
  • Location: Brighton, East Sussex

GEFS having none of it, a pretty hideous set of ensembles within a decent timeframe it must be said, although I would also say if the main GFS run is wrong then what chance do the ensembles have?

Answers on a postcard please.

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield

gFS 6z para totally at odds with its earlier run ie to the NNW.huge area of low pressure heading towards the UK ??

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

If the Para is anything to go by, most of any snowfall looks like being confined to the far northeast of Scotland - all-in-all a somewhat dreich and to the week?

Netweather GFS Image

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Posted
  • Location: Wyke regis overlooking Chesil beach.
  • Weather Preferences: Snowfall
  • Location: Wyke regis overlooking Chesil beach.
1 hour ago, s4lancia said:

Ever the optimist I may be, but I think we are down to 15%? for a notable snow 'event' for the masses, as a result of trough disruption passing under the NE block. Catacol's description of the block being 'an echo' is a really good one when looking at the current lack of background forcing. I just don't see enough to convince me the jet is going to play ball. Not for a little while longer anyway.

However... A Christmas Northerly though? Yep. Makes complete and utter sense to me now. This signal will grow stronger and stronger IMO. I expect to see some sharp dips towards the end of some of the GEFS members in the coming days and week.

Remember Winter 1963 (no direct comparisons intended) didn't get going until Boxing Day 1962...

Very true S4L the modelled Scandinavian high has never truly convinced me in terms of being strong. Nice to look at but an Xmas northerly would certainly tie with GP's suggestion of ignoring any numerical output that doesn't build hieghts to the Northwest in the approach to xmas

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Posted
  • Location: portsmouth uk
  • Weather Preferences: extremes
  • Location: portsmouth uk
44 minutes ago, Weathizard said:

GEFS having none of it, a pretty hideous set of ensembles within a decent timeframe it must be said, although I would also say if the main GFS run is wrong then what chance do the ensembles have?

Answers on a postcard please.

Yes I just looked awful gefs.

I just don't think the Scandinavian block is enough for the Atlantic onslaught.

Massive rain totals though and some seriously damaging winds.

Let's hope it's not to bad.

as a white Christmas would be disruptive,

but not as disruptive as flooding and gales.

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
17 minutes ago, Frosty. said:

Merry Christmas Netweather from the Gfs 6z operational...yes I've been drinking!:drunk-emoji:❄️:santa-emoji:

06_348_preciptype.png

06_348_ukthickness850.png

Sorry Karl...the Para run off with all your presents... an MUI is a serious offence!?:drunk:

Netweather GFS Image

Edited by Ed Stone
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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

This mornings ECM pressure run shows a lot of spread by the end of the week 

download.thumb.png.62e8029e5afabfa65f2091810cf61447.png

The 850 mean by the end of the week gets down to -3.5 whereas the op goes to -7.8

1702532496_download(1).thumb.png.91bd3f47d3cdd76f3058bbb8621824b0.png

Edited by Summer Sun
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Posted
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
  • Weather Preferences: continental climate
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow

Am I looking at things too simplistic with trying to understand the gist of stratospheric-tropospheric  interaction?

In next few days we are going to have Scandinavian blocking trying to establish itself. Around the same time a pulse of warming at 10hPa around Alaska is pushing the stratospheric polar vortex towards the same region where we have tropospheric heights- Scandi/western Russia(picture.1). 

Subsequently we loose the blocking over Scandinavia.

Then in  around  2 weeks time we see another pulse of stratospheric warming around eastern Siberia moving the core of polar vortex at 10hPa to Greenland/Iceland area(picture.2).  In the same time we see on the hemispheric view of 500mb height anomalies that the core of tropospheric polar vortex is moving in the same direction - towards Greenland(picture.3)

Am I making a false assumption of atmosphere in thinking that these stratospheric warmings are doing us no favors at all on short to medium term?

There might be a pot of gold towards February and March, but how about the month where winter really matters for most of us - a week before and around Christmas. Most of posters on here are excited when they see these stratospheric warmings appear, but are they not having the opposite effect at least in the context of December? 

 

Z_temp_10hpa_144.png

gfsnh-10-384.png

gensnh-21-1-384.png

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